Currently, the extraction and use of solar energy is not too strange problem for each of us. Solar energy is one of the promising green energy will be widely applied in human life in the future. This is a source of seemingly endless energy, easy to use and helps operators protect human habitat. And of course, solar battery is an important component in the use of energy sources of the future. Forum " Each week one invented "this week will review the important milestone in the process of formation and development of solar cells. all started from accidental discovery of the best engineers Smith ...
Starting
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It started with Willoughby Smith (1828-1891), a British electrical engineer. In 1848 Smith began working for the electric company to work Gutta percha is the development of the telegraph wires of iron and copper. 1849, he joined the project manage the installation of underground telegraph wires and he continued his work like that for several decades thereafter. Until ... 1873, Smith developed a method to check the continuity of the wire has been installed underground. To make the circuit test, you need a semi-resistive materials and high end, he chose selenium. On the theory of Smith, selenium perfectly suited to the requirements set forth by him. However, Smith discovered a problem arises: At night, the bar selenium to function properly with the requirements of Smith. Electrical conductivity of selenium significantly increased when exposed to strong light. To verify the cause, Smith was placed on the side bar of selenium in the box with sliding lid. When the lid is closed and can not reach the light, sound power is the highest selenium and strictly prevent the current task. But when the lid is slid out light to flood in, more current flows through the strengthening and increasing intensity of the lighting. Meanwhile, Smith has published his findings in the journal Nature to content "The effect of light on selenium through electricity transmission lines." The report has caused the attention of many scientists throughout Europe at that time. With his research, Smith was recognized as the first to discover the nature of the photovoltaic element selenium. This discovery has set the stage for the creation solar future. 1874, Scottish scientists with the laws of electromagnetism famous, James Clerk Maxwell wrote to a colleague that his internal text: "I witnessed the effects of light on selenium. thing that was unexpected. Dong heating can not react similarly. It is a great thing of the Sun." Discovering photovoltaic effect in solid materials then, Smith has made a series experiments to determine ngiem nature sunlight has the effect of selenium how to stick? The effects of heat or optical effects. In one experiment, he was placed in a trough bar selenium in shallow reservoirs. The water in the trough prevents the temperature from the sun but still retaining effects of selenium light up bar. Results of experiments suggest that, when had this kind of problem only retain heat and light from the Mostly, the reaction of selenium still sound like Smith first discovered. And finally, he has come to the conclusion that the selenium resistivity change according to light intensity. Later Smith, among many scientists continue to study the effects of light on selenium 2 scientists English: Professor William Grylls Adams and his student, Richard Evans Day. During the late 1870s, two people have done a lot of experiments with selenium. One of those experiments was a candle lit bar placed selenium used 1 inch. When the candle has been lit up, the needle on the power meter repeater equipment immediately respond. When light from the candle is covered, metal on electric meters away back into position 0. Rapid response was again reinforced by Smith concluded that the new light is the main factor affect the electrical conductivity of selenium bar. So if the influence of thermal effects, the needle in electrical instrumentation will move slowly without sudden increase or decrease. 2 Group researchers felt he had discovered an entirely new problem has never previously: Light has the ability to cause a "current" on a solid. Adams and Day has been named currents generated by the light is "photovoltaic."
First Module Invented
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| House inventor Charles Fritts American and the first photovoltaic module |
A few years later, the American inventor Charles Fritts made a big step forward in the technology successfully fabricated a photovoltaic module first in the world. With the first module, Fritts was wide and covered with a thin layer onto a metal plate. Then he used a thin gold leaves and semi-transparent plates covered up. As reported by Fritts, selenium module so you can make an electric current to create "continuous, stable and considerable intensity, ... not only with daylight, low light, but also works with the light bulb. With his success, Frotts optimistic model predicts that photovoltaic panels can replace his method to generate electricity by burning coal which is being widely used time. statement he was born 3 years after Thomas Edison created the method of producing electricity from heat by burning fossil fuels like coal, oil, ... Next, Fritts has sent a photoelectric Werner von Siemens for its inventor with a reputation comparable to Edison at the time. Prior currents of photovoltaic panels that generate Fritts, Siemens and other German scientists were impressed. they simultaneously presented photovoltaic panels for the National Academy of Prussian royal science. Siemens reported to the scientific world that "Americans Module presented to us, for the first time can directly convert energy amount of sunlight into electrical energy. " Siemens has said that photovoltaics is an important scientific discoveries and the most extensive. James Clerk Maxwell (1831-1879), Scottish physicist known for the fundamental laws of electric field, have strongly agreed with the statement of Siemens. Maxwell praised photovoltaic research as "an invaluable contribution to science."
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| Not only Siemens but Maxwell has yet to find an explanation to account for the phenomenon of photoelectric |
However, both Siemens and Maxwell still can not understand the nature of the photovoltaic phenomenon. Maxwell wondered: "Does the solar radiation is the cause of the problem or its causes chemical changes in selenium bar? And of course, Siemens also not explain the nature of this phenomenon and he has called "conduct a thorough investigation to determine the root causes of the phenomenon photovoltaic selenium bar depends on what factors?" There are very few scientists who responded to the call of Siemens. Nguyen This is due to the photoelectric detection seems to be contrary to the understanding of human science. At that time, it was only known that can convert thermal energy into electricity thanks to earlier detection of Edison. selenium But Adams and Day bar or "magic plates" of Fritts deemed unscientific and can not be true because not use heat to electricity. therefore, the majority of scientists are from continued refusal phenomenon photovoltaic research. however, scientists still have a "brave": George M. Minchin, professor of applied mathematics at technical colleges royal India. Minchin embarked on research to explain the photoelectric phenomenon. Minchin's action was time for the scientific community is unscientific and is a crazy job. In fact, Minchin came close to explaining the impact of selenium light up bar. Even so, there is no satisfactory explanation has been given. scientific community has rejected Minchin time of untapped potential photovoltaic after seeing the test results from one of Minchin. During testing, Minchin has placed photovoltaic modules on glass in a black box and measuring the heat inside the box. piloted by placing photovoltaic modules in a glass box black to absorb sales by Minchin sunlight made. Minchin has argued that: "It is clear that the black box has glass absorbs all the energy in sunlight and convert into heat inside the box. However, this may not exactly." Minchin believes that "there may be some form of solar energy being absorbed by the black surface. And something needs to be discovered. Only when scientists can measure energy of different wavelengths, the optical power problem is solved. " important discoveries of Einstein Along with views Minchin, Albert Einstein said that contemporary science has yet to detect and measure all forms of energy travel from the sun to Earth. In a bold study published in 1905, Einstein has raised an attribute of light that scientists previously not recognized. He discovered that light consists of "packets" of energy and he called it the quanta (photons is present).
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| Add an Einstein contribution to the development of mankind with the quantum theory of light, paving the way for future photovoltaic research. |
True to predict what Minchin, Einstein argued that the amount of energy that the light quanta will be expressed in different forms and depends on the wavelength of light. More specifically, the shorter the wavelength, the greater the energy. Shortest wavelengths can carry 4 times more energy than the longest wavelengths. Einstein's bold description of the nature of light, combined with the discovery of the electron mass has made scientists start Closer study of the effects of light. All these things are turning for the development of photovoltaics in the 19th century. Before all the mysteries that revolve around the sun and photovoltaic can be explained in the framework of science. In these types of materials such as selenium, the photon carries enough energy needed capable of electron impact on the weakest link and the other to control it moves the original trajectory. When the power cord is attached to the bar selenium, the electrons released by photons of energy will move in forming wires and power lines. The experiment began in the 19th century is called the photovoltaic phenomenon. Explaining clearly photovoltaic phenomenon has stimulated scientists to further research to find ways to generate a lower scale photovoltaic industries. Since then realize dreams mining and clean energy from the sun endless. Dr. Bruno Lange, German scientists should design each photovoltaic module similar to Fritt in 1931 was also predicted that "In a not too distant future, thousands of photovoltaic modules will be designed to convert solar energy into electricity. This can replace the hydroelectric power plants or thermal power, can make the cars Solar steam and can even be used for every household. " However, due to battery power that Lange made less efficient operation than the version of Fritt, only metabolize about 1 % energy from sunlight into electricity. This is not enough to justify the feasibility of exploiting solar energy on an industrial scale. pioneers in creating photovoltaic encountered failure compared with the initial hope was coined. However, all their efforts would not be totally useless. A contemporary Minchin also predicted that "the day will come when people will be able to obtain energy from the sun with high performance and even store them. This will make the steam engine and the type of Other engine completely extinct. " About next time, no breakthrough was recorded in the photovoltaic exploitation. Even the head of the energy group Westinghouse also said that "solar battery will not be able to attract engineers until the conversion efficiency of solar energy into electricity is at least 50% . the author of the book Photoelectricity and Its Applications (Optical energy and its applications) published in 1949 gave a pessimistic prediction that: "Only when the future discovery of a kind new substances, the new photovoltaics can harness solar energy for useful purposes for human beings. "
The First Perfect Solar Battery
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| Gerald Pearson, scientists at Bell Laboratories |
Everything revolves around the exploitation of photovoltaic seemed forever stopped until researchers discovered the possibilities of silicon. This is a major turning point in the development of solar cells. The researchers accidentally discovered the possibilities in the fabrication process of silicon transistors - the main component of every electronic device today. 2 scientists are Calvin Fuller and Gerald Pearson of laboratory Experimental famous Bell Laboratories (now AT & T Laboratories), were pioneers in the manufacture of silicon semiconductor diodes formed from the initial theory to practical fabrication. Pearson is the co-workers described as a man "of empirical experimentation." But Fuller, a chemist who contributed in no small part to the discovery of substances added to silicon to make it from a less conductive material becomes a conductor pros Vietnam. During the study, Fuller Pearson provides a piece of silicon that contains a small amount of gallium. The presence of gallium make available positively charged silicon area. According to Fuller's formula, when Pearson embedded silicon samples containing lithium gallium into the hot tank, silica flooded part of the solution is negatively charged. In the middle portion located adjacent negatively charged and the positively charged, an electric field strength will be formed. This is a pn structure where all the electrical activity occurs. Pn transition structure is the central component of semiconductor diodes and solar batteries. During the test phase gallium silicon sample, the sample Pearson connected with wires gallium silicon phase, put it in the shade lights to illuminate the specimen and use the ammeter to measure. And in this experiment appeared a phenomenon that Pearson amazed ... An electric current is created when light shines on silicon samples. This is random but detection is very important for solar cell current.
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| PN junction structure, the most important component of semiconductor diodes. Precise successfully fabricated solar battery perfect |
While Fuller and Pearson are researching innovative semiconductor diodes, also a scientist of Bell Laboratories, Daryl Chapin began to study the energy in the battery depletion when used in areas with high high humidity. In any other climate, traditional dry batteries will perform its function well. Only in areas where hot and humid tropical climate, the life cycle of the battery becomes shorter than when used in different climates. Laboratory Chapin tasked to find a different kind of battery power more feasible such as wind power, thermal power generators, steam, ... Chapin has proposed developing solar battery and suggestions were approved laboratory. late February 1953, Chapin began implementing photovoltaic research. To be able to put a solar panel on commercial exploitation, Chapin aims is to create a panels can generate electrical current capacity of 4.9 W per square meter and the conversion efficiency from solar energy to electricity is highest. The study by Chapin has spread to the ears of Pearson. He told Chapin about his accidental discovery of patterns and give Chaplin gallium silicon phase. Immediately, Chapin tested under sunlight and found Pearson's findings are absolutely correct. According to the measurement of Chapin, silicon solar cells form provided by Pearson conversion efficiency from optical power to electrical power is 2.3%, compared with 5 times the battery by selenium. Since then, Chapin moved to focus research and development of silicon solar cells. Based on his theory calculations, Chapin predict silicon solar cells can harness solar energy with efficiency up to 23% if achieved under ideal conditions. However, his initial goals set forth by the conversion efficiency of about 6%. This is the threshold at which the engineers of that time put out if you want to create a kind of photovoltaic and consider it to be a real source of electrical energy.
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| Callvin S. Fuller, Bo is coated onto silicon to create solar battery should complete the world first. |
However, despite a lot of testing done with different methods, Chapin has not progressed compared to the original. There are obstacles appear and seem insurmountable. Chapin and reconstruct the quantum theory of light Einstein as well as studies of previous semiconductor Pearson and Fuller. Finally, he realized something that should be thanks to the help of Fuller to bring a PN junction structure as close as possible to the pin surface. Besides, Chapin found that the surface of silicon wafers too shiny so will reflect a significant amount of light. Therefore, he chose to cover a translucent plastic. Next, he covered with a layer of butter on the top surface of the photovoltaic panels in order to obtain more photons. And the end result is exactly as solar panels Chapin goals laid out - there Milk 6% conversion. Group 3 scientists have reported studies with the Institute of National Academy of Sciences of the success achieved.
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| Group 3 scientists in an experiment with solar batteries (From left: Pearson, Chapin and Fuller) |
Finally, solar energy battery is officially a new energy source for humans. Since then until now, solar batteries continue to be refined and improved in order to enhance performance but simple fabrication methods and low cost. Numerous methods have been developed and applied to the end is the solar panels as we see today.
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